Despite recognition of the fundamental role of zinc (Zn2+) for growth and proliferation, mechanisms of how Zn2+deficiency arrests these processes remain enigmatic. We induced subtle intracellular Zn2+perturbations and tracked asynchronously cycling cells throughout division using fluorescent reporters, high throughput microscopy, and quantitative analysis. We found that Zn2+deficiency induces quiescence and Zn2+resupply stimulates cell-cycle reentry. By monitoring single cells after Zn2+deprivation, we found that depending on where cells were in the cell cycle, they either went quiescent or entered the cell cycle but stalled in S phase. Stalled cells were defective in DNA synthesis and had increased DNA damage levels, suggesting a role for Zn2+in maintaining genome integrity. Finally, we found that Zn2+deficiency-induced quiescence does not require the cell-cycle inhibitor p21. Overall, our study provides new insights into when Zn2+is required during the mammalian cell cycle and the consequences Zn2+deficiency.